diff --git a/server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogramTests.java b/server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogramTests.java
index f487b783ae159..729ff5368daac 100644
--- a/server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogramTests.java
+++ b/server/src/test/java/org/elasticsearch/search/aggregations/bucket/histogram/InternalAutoDateHistogramTests.java
@@ -155,7 +155,7 @@ protected void assertReduced(InternalAutoDateHistogram reduced, List<InternalAut
 
         int roundingIndex = reduced.getBucketInfo().roundingIdx;
         RoundingInfo roundingInfo = AutoDateHistogramAggregationBuilder.buildRoundings(null, null)[roundingIndex];
-        Rounding.Prepared prepared = roundingInfo.rounding.prepare(lowest, highest);
+        Rounding.Prepared prepared = totalBucketConut > 0 ? roundingInfo.rounding.prepare(lowest, highest) : null;
 
         long normalizedDuration = (highest - lowest) / roundingInfo.getRoughEstimateDurationMillis();
         int innerIntervalIndex = 0;